A method of biochemical analysis of a mixture of components with the use of magnetic particles is known [Ch. B. Kriz, K. Radevik, D. Kriz, Magnetic Permeability Measurements in Bioanalysis and Biosensors/Anal. Chem. 68, 1996, pp. 1966-1970], which includes the following:
making use of a chosen component attached to magnetic particles;
exposing said magnetic particles to a magnetic field,
recording a signal due to the magnetic induction produced by said magnetic particles as a result of their exposure to the magnetic field,
judging the content of the analyte in the mixture being analysed from the value of said signal.
According to this method, one introduces particles into a specimen of the mixture to be analysed, which particles carry recognising elements that selectively bind the analyte. Besides, in the mixture being analysed there should be a chosen component attached to magnetic particles. This component binds selectively to the analyte after binding of the latter to the recognising elements, or competes with the analyte for binding to the recognising elements. In exceptional cases when the analyte contains magnetic particles, the chosen component can be the analyte itself.
As this takes place, this method necessarily includes removing from the specimen such magnetic particles that have appeared to be unbound to the carrier particles after the course of the reactions mentioned above. To do so, the specimen is subjected to sedimentation, spinning, and rinsing with a binding buffer solution. Then a certain dose of the specimen is placed in a test-tube, which is inserted in an inductance coil. From the change of the magnetic induction of the coil after inserting the specimen into it the content of the analyte in the medium being analysed is judged.
The drawback of this analogue consists in its high complexity and low throughput because of a large number of operations. This leads also to high cost, insufficient reliability and low accuracy of the results obtained.
The closest to the proposed method is an analogue-method of polynucleotide and protein analysis using magnetisable moieties [U.S. Pat. No. 5,656,429 of Dec. 8, 1997, Polynucleotide and protein analysis method using magnetizable moieties, Int. Cl.: C12 Q 1/68, U.S. Cl.: 435/6,], which comprises the following operations:
choosing a component for attaching magnetic particles to it or a component that is already attached to magnetic particles, this chosen component being either the analyte or another component that allows judging the content of the analyte in the mixture being analysed,
spatially arranging said chosen component,
attaching magnetic particles to said chosen component or using said chosen component that is already attached to magnetic particles,
exposing said magnetic particles to a magnetic field,
recording a signal due to the magnetic induction produced by said magnetic particles as a result of their exposure to the magnetic field,
judging the content of the analyte in the mixture being analysed from the value of said signal.
In doing so, one distributes components in a prescribed manner (e.g., by electrophoresis) on the surface of a substrate according to the molecular size and the quantity of the components in the mixture being analysed. Magnetic particles are attached to one or another component of the mixture before or after distributing the components on the substrate surface. Then one records the resulting distribution by magnetic reading from the substrate surface similarly to that one reads information from a magnetic disk. From said distribution one obtains information on the content of one or another component in the mixture being analysed. To enable the magnetic reading, the particles are magnetised by a dc magnetic field before or after distributing them on the substrate surface. The magnetic reading itself consists in the measurement of the magnetic induction resulting from the residual magnetisation of the particles. An important merit of the analogue-method is the spatial arranging of magnetic particles that are bound with the analyte or the chosen component. This arranging takes place on the substrate surface in a close proximity to a magnetic reader. Consequently, the reliability of the results is increased, the dimensions of the required apparatus are minimised, and compatibility of the apparatus with microelectronics technologies is ensured.
The drawbacks of this analogue-method are low sensitivity of the method and low accuracy of the results it yields, due to a number of reasons. These are: first, small concentration of the magnetic particles being recorded, which are “spread” on the substrate surface; second, very small residual magnetisation of known particles of micron and submicron size; and, third, well-known negative features of dc measurements. The mentioned reasons result in narrow application area of this method.
An analogue-apparatus for reading results is known for the method of biochemical analysis of a mixture of substances, using magnetic labels [Ch. B. Kriz, K. Radevik, D. Kriz, Magnetic Permeability Measurements in Bioanalysis and Biosensors/Anal. Chem. 68, 1996, pp. 1966-1970], which comprises:
magnetic particles attached to a chosen component of the mixture being analysed, directly or through an intermediate material;
a magnetic field generator, within which action said magnetic particles are situated;
a meter of the magnetic induction produced by said magnetic particles;
an output signal receiver;
a block generating the result, which input is connected to the output of the output signal receiver.
In this apparatus the magnetic induction meter, which is made as an inductance coil, is inserted in one arm of a bridge circuit, which input is connected to the output of the magnetic field generator and the input of the circuit is connected to the input of the output signal receiver.
The operation of this analogue-apparatus relies upon that the presence of magnetic particles in the sample being analysed and situated inside the inductance coil, which serves as the magnetic induction meter, leads to a change in this inductance and, hence, to a misbalance of the bridge circuit. This causes the generation of the output signal of the discussed apparatus.
The drawbacks of this analogue-apparatus are its high complexity and low throughput because the bridge should be precisely balanced for each new measurement. This also leads to high cost and, taking into account environmental temperature instabilities (especially in portable variants of the apparatus), to low accuracy of the results obtained.
The closest to the proposed apparatus is analogue-apparatus used for information reading in the polynucleotide and protein analysis method using magnetisable moieties [U.S. Pat. No. 5,656,429 of Dec. 8, 1997, Polynucleotide and protein analysis method using magnetizable moieties, Int. Cl.: C12 Q 1/68, U.S. Cl.: 435/6], which comprises:
a chosen component of the mixture being analysed, said component being spatially arranged in a prescribed manner;
magnetic particles attached to the chosen component of the mixture being analysed directly or through an intermediate material;
a magnetic field generator, within which action said magnetic particles are situated;
a meter of the magnetic induction produced by said magnetic particles;
an output signal receiver;
a block generating the result, which input is connected to the output of the output signal receiver.
Besides, the components of the mixture being analysed are distributed on the surface of a substrate according to their molecular size, the magnetic field generator and the magnetic induction meter enable generation and, respectively, recording of a signal constant in time.
The operation of the analogue-apparatus relies upon that the magnetic particles attached to one or several chosen components of the mixture being analysed, and distributed along the substrate surface, acquire a residual magnetisation resulting from their exposure to a dc magnetic field. Then by means of a dc magnetic field meter, e.g., a Hall sensor, one records the distribution of the magnetic induction caused by the residual magnetisation on the substrate surface. From this distribution one determines the amount of magnetic particles attached to one or another component of the mixture being analysed, and the content of this component in the mixture.
The drawbacks of this analogue are limited sensitivity of the apparatus and low accuracy of the results obtained. These are due to known negative features of dc measurements, low value of residual magnetisation, and low concentration of magnetic particles, which are spread on the surface of a substrate. The application area of this apparatus is rather narrow, too.
To conclude, the wanted technical result consists in rising signal-to-noise ratio and, hence, increasing measurement accuracy, enhancing sensitivity of the method and apparatus, improving reliability of the data obtained, along with lowering the costs of experiments owing to reduction of the operation number and time needed, amount and dimensions of the apparatus, and, besides, in developing mobile, cheap, high-throughput laboratories for mass tests, in improving the operational flexibility of the method and apparatus and extending their application area.